Surgical staplers have been used for over a century for providing leak-proof and hemostatic wound closures. See, for instance, “History of Mechanical Stapling”, pages 3–7 in Atlas of Surgical Stapling, Feil/Lippert/Lozac'h/Palazzini (eds.). More recently, circular staplers have been developed, having particular use in gastrointestinal surgery to facilitate inverted end-to-end, end-to-side and side-to-side anastomoses. (See pages 19–21, Atlas of Surgical Stapling cited above).
Surgical stapling instruments typically have a mechanism for firing a plurality of staples from a staple holding cartridge, and an anvil disposed opposite the staple cartridge against which the staples are formed. Such instruments include, for example, linear staplers, which typically apply one or more parallel rows of staples, and circular staplers, which typically apply one or more concentric and circular rows of staples. In use, the surgeon will place tissue between the staple cartridge and anvil and, by firing the instrument, cause the staples to become clenched to the tissue.
Circular staplers are known and have been successfully used in surgical procedures for many years. Commercially available instruments include the CEEA™. circular stapler, manufactured by United States Surgical Corporation, Norwalk, Conn., and the ILS™ circular stapler, manufactured by Ethicon, Inc., Blue Ash, Ohio. These instruments are typically indicated for use in gastric and esophageal surgery wherein tubular organs are joined to other anatomical structures.
In one common procedure, known as end-to-end anastomosis, a portion of the intestinal tract is removed (i.e., due to the presence of disease such as cancer) and the remaining ends are rejoined by using a circular stapler. To join the tubular structures, one end of intestine is secured about an anvil and the other end of intestine is held in place adjacent a staple cartridge. Preferably, the anvil has a shaft that is removably connected to the instrument. Once the anvil shaft is secured to the instrument, the anvil is drawn into close approximation to the stapling cartridge. The instrument is then fired to cause the staples to pass through tissue of both organs and become formed against the anvil. During the firing step, a circular knife is advanced to cut tissue inside the staple line, thereby establishing a passage between the organs. After firing, the instrument is typically removed by withdrawing the anvil through the staple line, after which the surgeon will carefully inspect the surgical site to ensure a proper anastomosis (joining) has been achieved.
While circular staplers have been extremely helpful in a number of surgical procedures, when used alone they are prone to creating a number of complications. An early survey of stapler-related complications revealed that in the 3594 end-to-end anastomoses conducted, intraoperative complications were reported in 15.1% of patients and included anastomotic leak, tear during stapler extraction, bleeding, and other complications. L. E. Smith, “Anastomosis with EEA stapler after colonic resection” Dis. Colon Rectum 24, 236 (1981). More recent studies have indicated that postoperative leakage, which can be quite dangerous in gastrointestinal tissue, continues to be a significant problem.
On a different subject, a variety of references teach the preparation of “buttress,” “pledget” or “reinforcing” materials for use in combination with conventional surgical staplers. See generally, Applicant's own U.S. Pat. Nos. 5,503,638, 5,549,628, 5,575,803, 5,752,965, 5,782,914 and 6,312,474.
By comparison, relatively few references suggest the use of buttress materials for use with circular staplers. Presumably, this is due to the problems inherent in positioning and using such materials, particularly since neither the shape of a circular stapler, or the demands of its use, are conducive to the placement or use of conventional buttress materials (e.g., pledgets). For instance, U.S. Pat. No. 6,273,897, which discloses a surgical buttress for use with linear staplers, mentions immediately before the claims that “the present invention may be similarly utilized in conjunction with other types of surgical staplers and cutters. For example, a circular stapler . . . may be suitably modified to provide buttresses on the staple cartridge and the anvil.”
On a separate subject, Applicants have also previously described the preparation and use of “preformed” tissue implants. See published International Application No. WO 99/48540, the disclosure of which is incorporated herein by reference.
What is clearly needed are materials and methods for providing surgical staple lines, and particularly circular staplers, having improved properties such as staple line strength and buttress seal.